Wii (Wii)NPD clarified Wii's & X360's 3rd party #CNet - August 12, 2008
Submitted by mrahaju (9)
at 7:05PM PST on August 12, 2008
According to NPD's Anita Frazier, in the first 20 months of availability (the entire tally of sold units so far), the Wii "sold 60 million total S/W, 33 milion is third party. This does not include Wii Sports"
During its first 20 months of availability, the Xbox 360 sold "35 million software units, 29 Million is third party"
Over its entire lifespan Xbox 360 has sold 82 million units total (67 million units third party)
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I think that it is always harder to get a lot of sales in the first year of a next generation timeframe. The hardware is new and there are not a lot of releases. Developers had more time to develop for Wii, so naturally more games were released in its 1st year. Wii also benefited from being low tech, so that games could be made more cheaply $, faster, and upgraded ports + remakes.